Systolic time intervals in normal Pakistani subjects: correlation with heart rate and regression analysis

Systolic time intervals [STI] were determined from simultaneous fast speed recording of the electrocardiogram [Ecg II], phonocar diogram [PCg] and carotid arterial pulse [CAP] tracing in 25 normal adults subjects [11 males and 14 females]. STI were then correlated with heart rate as well as with R-R interval separately for male and female groups. All STIs were related, linearly and inversely, to heart rate but direct linear relationship was found with R-R interval. Total electromechanical systole [Q-S2 interval] and left vertricular ejection time [LVET] wer significantly related to heart rate [inversely] and also to R-R interval [directly]. However pre-ejection heart rate or R-R interval. Appropriate regression equations were derived for STI with heart rate and R-R interval as an independent variables and were found statistically significant to predict values from observed heart rate or R-R interval except for PEP/LVET ratio which was not significant statistically. This should that PEP/LVET ratio is not affected by heart rate in the range of 52-110 beats per minute. Therefore, no correction of PEP/LVET ratio is needed in this range. Hence this ratio can be used for measuring left ventricular function. However all other STI should be corrected for observed heart rate in each subject